1. Field of the Invention
The present invention relates to a mirror for a laser scanning device, and, more particularly, to a mechanism for rotating a mirror of a laser scanning device.
2. Description of the Related Art
In a typical compact laser scanner device of the type commonly found in laser printers, a scanned laser beam is directed via optical fold mirrors to be incident upon a photoconductor drum. Such optical fold mirrors are commonly held in place by flat spring clips that provide a force in a direction to bias the optical fold mirror against three support mounts protruding from the laser scanner housing. These protrusions are usually located at the ends of the optical fold mirror in the main scanning direction. Two of these protrusions, one on each end, are usually fixed while the third is adjustable, thus allowing for small adjustments of the optical fold mirror. Common means of obtaining adjustments include screws and cams.
The main difficulty associated with the above-described mounting scheme is ensuring that the mirror rotates about its intended axis of rotation. To preserve the performance of the optical system, it is essential that the mirror rotates about an axis that is co-linear with the line created by the intersection of the scan plane and the plane of the reflecting surface of the fold mirror, hereinafter referred to as the fold line.
This is not achievable in the above-described mirror mounting scheme because the fixed mirror supports must be offset in the cross scan direction by approximately half the width of the mirror in order to provide a stable mirror mount. This inherently creates a rotation axis that is skewed to the fold line. In addition, it is possible for the fold mirror to not rotate about this skewed line at all and, instead, rotate about the hard stops that locate the mirror in the cross scan direction. This occurs when the clamp force in the cross scan direction is sufficiently high, thus developing a frictional force between the mirror and the hard stops that is greater than the force exerted by the bias flat spring.
What is needed in the art is a device for locating and fixing an optical fold mirror to a housing of a laser scanner device to ensure that the mirror rotates about its intended axis.
The present invention provides a mirror mounting arrangement that allows the optical fold mirror to rotate about an axis co-linear with the fold line and, subsequently, be held in its adjusted position.
The invention comprises, in one form thereof, an electrophotographic machine mirror assembly including a mirror having two opposite ends and a reflective surface. A laser device scans a laser beam along the reflective surface to define a fold line thereon. The fold line extends substantially between the two opposite ends of the mirror. At least one fixed mounting device has a support surface. At least one rotational device is attached to the mirror. The at least one rotational device has an arcuate surface defining an imaginary circle and engaging the support surface of the at least one fixed mounting device. The imaginary circle has a center substantially coincident with the fold line of the reflective surface. The at least one rotational device rotates about the center of the imaginary circle to thereby rotate the mirror about the fold line.
An advantage of the present invention is that the mirror rotates about an axis that is co-linear with the fold line.
Another advantage is that the arcuate surface of the mirror mounts provide smooth and easily controllable movement of the mirror to thereby enable accurate positioning thereof.